312 THE ADDRESSES, LECTURES, ETC., OF 



in the outer solar atmosphere has been given by Professor Stoney, 

 the Astronomer Royal for Ireland, and by Mr. R. Meldola in an 

 interesting paper communicated by him to the " Philosophical 

 Magazine " in June, 1878. 



As regards the sufficiency of an inflowing stream of dissociated 

 vapours to maintain solar energy, the following simple calculation 

 may be of service. Let it be assumed that the stream flowing in 

 upon the polar surfaces of the sun flashes into flame when it 

 has attained the density of our atmosphere, that its velocity at 

 that time is 100 feet per second (the velocity of a strong terres- 

 trial wind) and that in its composition only one-twentieth part 

 is hydrogen and marsh gas in equal proportions, the other 

 nineteen-twentieths being made up of oxygen, nitrogen, and 

 neutral compounds. It is well known that each pound of 

 hydrogen develops in burning about 60,000 heat units, and 

 each pound of marsh gas about 24,000 ; the average of the two 

 gases mixed in equal proportion would yield, roughly speaking, 

 42,000 units ; but, considering that only one-twentieth part of the 

 inflowing current is assumed to consist of such combustible matter, 

 the amount of heat developed per pound of inflowing current 

 would be only 2,100 heat units. One hundred cubic feet, weigh- 

 ing eight pounds, would enter into combustion every second upon 

 each square foot of the polar surface, and would yield 8 x 60 x 

 60 x 2100 = 60,480,000 heat units per hour. Assuming that one- 

 third of the entire solar surface may be regarded as polar heat- 

 receiving surface, this would give 20,000,000 heat units per square 

 foot of solar surface ; whereas according to Herschel's and 

 Pouillet's measurements only 18,000,000 heat units per square 

 foot of solar surface are radiated away. There would thus be no 

 difficulty in accounting for the maintenance of solar energy from 

 the supposed source of supply. On the other hand I wish to 

 guard myself against the assumption that appears to have been 

 made by some critics, that what I have advocated would amount 

 to the counterpart of " perpetual motion," and therefore to an 

 absurdity. The sun cannot of course get back any heat radiated by 

 himself which has been turned to a purpose ; thus the solar heat 

 spent upon our earth in effecting vegetation must be absolutely lost 

 to him. 



My paper presented to the Royal Society was accompanied by a 

 diagram of an ideal corona, representing an accumulation of 



